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From: Chandramouli Parasuraman on 4 May 2010 06:59
Hi,

I'm new to ruby, and I am trying to add all the natural numbers below
one thousand that are multiples of 3 or 5. (exercise from ProjectEuler)

Here's my code:

class Array
def sumNumbers
sum = 0
self.each_with_index { |n, i|
if ((self[i] % 3) == 0 || (self[i] % 5) == 0)
sum += self[i]
end
}
sum
end
end

numbers = [1..1000]
print "Sum of natural numbers till 1000 that are multiples of 3 or 5 is
" + numbers.sumNumbers

When I try to execute this, I get this error:

SumOfMults.rb:5:in `block in sumNumbers': undefined method `%' for
1..1000:Range
(NoMethodError)
from SumOfMults.rb:4:in `each'
from SumOfMults.rb:4:in `each_with_index'
from SumOfMults.rb:4:in `sumNumbers'
from SumOfMults.rb:14:in `<main>'

Not sure how self[i] is actually treated as a Range. Can you please let
me know what's wrong in my code?

Thanks,
Mouli
--
Posted via http://www.ruby-forum.com/.

From: Alex DeCaria on 4 May 2010 07:28

> numbers = [1..1000]

In your code, numbers is an array with a single element. That single
element is a range of numbers from 1..1000. Instead, don't you want
numbers to be an array like [1, 2, 3, 4, 5, ..., 999, 1000]? You can
create this array by

numbers = Array.new(1000) { |i| i+1 }

--Alex
--
Posted via http://www.ruby-forum.com/.

From: Brian Candler on 4 May 2010 07:37
Alex DeCaria wrote:
>
>> numbers = [1..1000]
>
> In your code, numbers is an array with a single element. That single
> element is a range of numbers from 1..1000. Instead, don't you want
> numbers to be an array like [1, 2, 3, 4, 5, ..., 999, 1000]? You can
> create this array by
>
> numbers = Array.new(1000) { |i| i+1 }

or:

numbers = (1..1000).to_a
--
Posted via http://www.ruby-forum.com/.

From: Robert Dober on 4 May 2010 07:39
On Tue, May 4, 2010 at 12:59 PM, Chandramouli Parasuraman
<contactmouli(a)gmail.com> wrote:
I would be more rubymatic here ;)
1000.times.inject{ | sum_so_far, next_number |
if (next_number % 3).zero? || (next_number % 5).zero?
sum_so_far + next_number
else
sum_so_far
end
}

It might be exaggerated to use the implicit form of inject just
because the first value is zero (it will be passed to sum_so_far in
the first iteration)

inject(0){ | sum_so_far, next_number |
}
might have been more readable

HTH
R.




--
The best way to predict the future is to invent it.
-- Alan Kay

From: Robert Dober on 4 May 2010 07:43
On Tue, May 4, 2010 at 1:37 PM, Brian Candler <b.candler(a)pobox.com> wrote:
<snip>
> numbers = (1..1000).to_a

or even [*1...1000] ( remark that 1000 must not be in the solution here ).
However I feel it is completely inadequate to the solution to create
an array of 999 numbers.

R.

> --
> Posted via http://www.ruby-forum.com/.
>
>



--
The best way to predict the future is to invent it.
-- Alan Kay

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